Re: Potential static analysis ideas

From: "NeilBrown" <neilb@suse.de>
To: "Linus Torvalds" <torvalds@linux-foundation.org>
Cc: "James Bottomley" <James.Bottomley@hansenpartnership.com>,
	"Geert Uytterhoeven" <geert@linux-m68k.org>,
	"Hannes Reinecke" <hare@suse.de>,
	"Julia Lawall" <julia.lawall@inria.fr>,
	"Arnd Bergmann" <arnd@arndb.de>,
	"Laurent Pinchart" <laurent.pinchart@ideasonboard.com>,
	"Dan Carpenter" <dan.carpenter@oracle.com>,
	ksummit@lists.linux.dev
Subject: Re: Potential static analysis ideas
Date: Tue, 27 Jul 2021 07:53:49 +1000	[thread overview]
Message-ID: <162733642991.4153.12959746307003856354@noble.neil.brown.name> (raw)
In-Reply-To: <CAHk-=wh1-KNDZn38e7OFdkGCRmtAx=wVp0ZRSKHh6zioWoZV+w@mail.gmail.com>

On Tue, 27 Jul 2021, Linus Torvalds wrote:
> 
> Anyway, gcc has this completely ass-backwards "nonnull" function
> attribute, sadly it's pure garbage. It's not a "type of this pointer"
> thing, it's a "this function does not take NULL as argument X" thing.

Yeah, I found that annoying too.  It seems to be purely about
optimization.  Marking a function parameter as "nonnull" means the
compiler can optimize away any tests against NULL.

> 
> We could relatively easily add a "__nonnull" type attribute  (and
> "__errptr") and parse it in sparse, but it would be _all_ over the

sparse already parses __attribute__((safe)) which seems to mean
something like __nonnull.  It needs a bit of work to make it useful.

> place, and without real compiler support it's probably not worth it
> (people already don't run sparse all that much, and a lot of the
> things sparse can warn about are too verbose to be be used in
> practice).

I'm not convinced that "real compiler support" is essential.
checkpatch.pl does provide some value despite not being "real compiler
support" and not being mandated.

NeilBrown